Influence of casting direction on chloride-induced rebar corrosion
ABSTRACT: The steel/concrete interface is one of the major influencing factors for chloride-induced reinforcement corrosion. Its properties are highly dependent on conditions during casting, compaction and the transformation from fresh concrete to a solid material. The present paper demonstrates the influence of casting direction on chloride-induced corrosion. Reinforced concrete samples were subjected to chloride exposure by wetting/drying cycles until depassivation of the steel was detected. As chloride penetration was monitored with embedded chloride ion selective electrodes (chloride sensors), information in terms of the free chloride ion activity in the pore solution was obtained. After depassivation, the specimens were split for visual examination and acid-soluble chloride analysis. It was observed that corrosion always initiated on the lower rebar side with respect to casting direction. Macroscopic defects such as air voids are not necessarily the sites at which pitting initiates. The results are discussed with regard to both total and free chloride contents.